Margot, BBC Four

If Margot Fonteyn and Rudy Nureyev were the most massively important people who ever existed in ballet, then the most massively important question that ever existed in ballet was, did they sleep together? Last night Margot got this over pleasingly quickly. There was the quivery BBC anno at the start that there would be scenes “of a sexual nature”, and hop-skip-jump the couple were at it like rabbits straight after their first performance together.

After that things got considerably more complicated, and far more enjoyable. Following the disaster that was Gracie! last week, I fully expected catastrophe from Margot. This is after all a "Woman We Loved", a BBC series definition that has been increasingly called into one-word question by the films about cold Enid, deceptive Gracie, and now gullible Margot. All pretenders, the lot.

The casting announced beforehand had fully primed me, along with all balletomania, contra: Anne-Marie Duff as Margot, with her huge chin and legs! Camp old Derek Jacobi as her choreographer Frederick Ashton! Two chaps we never heard of as Rudy Nureyev and Tito Arias? In fact, though the dancing by the actors was inevitably risible, the story told was far from risible, even if lots of it was gleefully made up - and some of the acting was just fine.

Fonteyn, after all, surely wins the palm for the most sensational married life of any ballerina in modern times. Most speculation about her affections circle around Rudy; Otto Bathurst’s film with bold unorthodoxy chose to place him as essentially Margot's walker, a pretty, narcissistic ballet partner in whom she could cosily confide her marital worries, and over whom she rapidly recovered when she started discovering leather boys on her staircase in the middle of the night. Perhaps he was even inessential to her, deep down.

The emotional focus that emerged was the unsolved mystery of her relationship with Roberto “Tito” Arias, the slimy Panamanian crook-politico whom she married in her mid-thirties, who cheated constantly on her, and who finally, by getting shot and paralysed by a fellow Panamanian crook-politico, ensured that Margot would forever be tethered to an increasingly ignoble performing career.

There is far too much here for a TV film of a mere hour and a half, and so it chose to home in on Duff’s extraordinarily large, all-absorbing eyes and brittle smile, portraying Fonteyn as a gullible, half-educated, vulnerable child-woman whose mother never left her side, who hadn’t the slightest idea what her romantic, exotic husband was up to, and who only really enjoyed being on stage playing let’s-pretend-we’re-not-real.

In the sense that the ballerina, with all her grown-up art and ability, has to devote her life to playing let’s-pretend, seriously, for all of us, Duff conveyed this idiot-savant act brilliantly. It’s true among many great ballerinas that a lack of intellectual curiosity far from blighting their artistry serves it, and I thought she nailed that.

Trouble was that the writer, Amanda Coe, forgot that the PR had said this was about Margot ’n' Rudy (hopelessly baby-faced Michiel Huisman - without the nostrils of genius, whatever de Valois may have said), and she - and we - were more intrigued by the dancer’s relationship with her rotter husband, Tito Arias (a deliciously cruel and old-fashioned Con O'Neill), a man who wouldn’t last a sandwich with today’s ballerinas.

As a result, we got a far more tantalisingly dappled light upon the mystery that might have been Margot. Conventionally, she had been a sexual goer as a rising ballerina - there were a few too many inelegant bits of back-history scripted: “You got sewn up for your marriage, didn’t you?” - who got stuck on the shelf in career glory, turned to an old flame in desperation in her mid-thirties, and was on the brink of divorcing him for his philandering, if not for his guerrilla run-running. The surprise turn was when he got shot and Margot became his slave.

Or did she? One of the good things in the script, which was stuffed like a spotted dick with aperçus from splendid recent biographies of Fonteyn and Ashton, was the Ashton comment that now Tito was paralysed, Margot had him exactly where she wanted him. (One of the stories missed in this script was Ashton's own obsession with Margot.)

There was a marvellous exchange as Tito was stretchered, immobile and grey-lipped, into Stoke Mandeville, and Margot told him she had, reluctantly, to leave him to dance in Spoleto. “They paying you in lire?” he mouthed, effortfully. “Sterling, darling, as you said,” she whispered, kissing him.

Duff and O’Neill were mesmerising together, but the scene-stealing came from the great Penelope Wilton as Fonteyn’s suburban mother BQ (for Black Queen), and the crackling Lindsay Duncan, who captured the icy, witty command of Ninette de Valois to a V.

Lit lusciously to cover up a certain parsimony in the art-direction (though with some notably good music choices), this was a bad film about a ballerina but a rather good one about a child-woman who never really fell in love with anyone or anything other than the stage. Plausible drama, and plausible reality too.

Margot is repeated on BBC Four on Friday 4 December at 1.25am and Saturday at 9pm. Also on BBCiPlayer till 11pm on Monday 7 December.

MacMillan's ballet Romeo and Juliet with Fonteyn and Nureyev is broadcast on BBC Four on Friday 4 December at 8pm, followed at 10pm by the documentary Nureyev: From Russia With Love.

Read theartsdesk interview with Anne-Marie Duff.